Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.94	11.557%	$196.2734	$196.27	$196.25	$196.30
Purchase #2	$240.55	11.823%	$268.9902	$268.99	$269.00	$269.00
Purchase #3	$21.79	8.758%	$23.6984	$23.70	$23.70	$23.70
Purchase #4	$158.42	7.851%	$170.8576	$170.86	$170.85	$170.90
Purchase #5	$72.88	8.181%	$78.8423	$78.84	$78.85	$78.80
Purchase #6	$60.58	3.335%	$62.6003	$62.60	$62.60	$62.60
Purchase #7	$210.70	8.157%	$227.8868	$227.89	$227.90	$227.90
7 purchase totals =	$940.86		$1,029.1490	$1,029.15	$1,029.15	$1,029.20